Poly(aryl ether ketone)s are a known class of engineering polymers. Several poly(aryl ether ketone)s are highly crystalline with melting points above 300.degree. C. Two of these crystalline poly(aryl ether ketone)s are commercially available and are of the following structure. ##STR1##
Over the years, there has been developed a substantial body of patent and other literature directed to formation and properties of poly(aryl ethers) (hereinafter called "PAE"). Some of the earliest work, such as by Bonner, U.S. Pat. No. 3,065,205, involves the electrophilic aromatic substitution (e.g., Friedel-Crafts catalyzed) reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether. The evolution of this class to a much broader range of PAE's was achieved by Johnson et al., Journal of Polymer Science, A-1, vol. 5, 1967, pp. 2415-2427; Johnson et al., U.S. Pat. Nos. 4,107,837 and 4,175,175. Johnson et al. show that a very broad range of PAE can be formed by the nucleophilic aromatic substitution (condensation) reaction of an activated aromatic dihalide and an aromatic diol. By this method, Johnson et al. created a host of new PAE's including a broad class of poly(aryl ether ketones), hereinafter called "PAEK'S".
In recent years, there has developed a growing interest in PAEK's as evidenced by Dahl, U.S. Pat. No. 3,953,400; Dahl et al., U.S. Pat. No. 3,956,240; Dahl, U.S. Pat. No. 4,247,682; Rose et al., U.S. Pat. No. 4,320,224; Maresca, U.S. Pat. No. 4,339,568; Atwood et al., Polymer, 1981, vol. 22, August, pp. 1096-1103; Blundell et al., Polymer, 1983, vol. 24, August, pp. 953-958, Atwood et al., Polymer Preprints, 20, No. 1, April 1979, pp. 191-194; and Rueda et al., Polymer Communications, 1983, vol. 24, September, pp. 258-260. In early to mid-1970, Raychem Corp. commercially introduced a PAEK called Stilan.TM., a polymer whose acronym is PEK, each ether and keto group being separated by 1,4-phenylene units. In 1978, Imperial Chemical Industries PLC (ICI) commercialized a PAEK under the trademark Victrex PEEK. As PAEK is the acronym of poly(aryl ether ketone), PEEK is the acronym of poly(ether ether ketone) in which the 1,4-phenylene units in the structure are assumed.
Thus, PAEK's are well known; they can be synthesized from a variety of starting materials; and they can be made with different melting temperatures and molecular weights. The PAEK's are crystalline, and as shown by the Dahl and Dahl et al. patents, supra, at sufficiently high molecular weights they can be tough, i.e., they exhibit high values (&gt;50 ft-lbs/in.sup.2) in the tensile impact test (ASTM D-1822). They have potential for a wide variety of uses, but because of the significant cost to manufacture them, they are expensive polymers. Their favorable properties class them in the upper bracket of engineering polymers.
PAEK's may be produced by the Friedel-Crafts catalyzed reaction of aromatic diacylhalides with unsubstituted aromatic compounds such as diphenyl ether as described in, for example, U.S. Pat. No. 3,065,205. These processes are generally inexpensive processes; however, the polymers produced by these processes have been stated by Dahl et al., supra, to be brittle and thermally unstable. The Dahl patents, supra, allegedly depict more expensive processes for making superior PAEK's by Friedel-Crafts catalysis. In contrast, PAEK's such as PEEK made by nucleophilic aromatic substitution reactions are produced from expensive starting fluoro monomers, and thus would be classed as expensive polymers.
These poly(aryl ether ketone)s exhibit an excellent combination of properties; i.e., thermal and hydrolytic stability, high strength and toughness, wear and abrasion resistance and solvent resistance. Thus, articles molded from poly(aryl ether ketone)s have utility where high performance is required. However, in some applications such as those where the poly(aryl ether ketone) is to be used as a thermoplastic composite matrix resin, its glass transition temperature (Tg) may not be as high as desired for the particular application. This is because polymers, even crystalline polymers, exhibit excessive loss of modulus, strength and creep resistance above their Tgs. This loss in properties may not be acceptable in cases where the materials are to be used as thermoplastic composite matrix resins.
Polyimides are a well known class of polymers. They are described by Cassidy, et al. in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., Vol. 18, pp. 704-719. C. Arnold, Jr., in the Journal of Polymer Science; Macromolecular Reviews, Vol. 14, pp. 265-378 (1979) devotes a portion of the article entitled: "Stability of High-Temperature Polymers", at pp. 322-333, to polyimides. They are also discussed by Elkin in Stanford Research Institute Report Number 86 (Menlo Park, Calif.) entitled "High Temperature Polymers" (1973). The physical and chemical characteristics of polyimides have been well documented.
In general, polyimides (especially aromatic polyimides) have excellent heat resistance but are difficult to process. According to P. E. Cassidy et al. (cited above), "wholly aromatic polyimide molding powders must be fabricated by sintering at high temperature and pressure". Injection molding and extrusion are thus not possible. J. M. Aducci in Polyimides, K. L. Mittal, Editor, 1984, published by Plenum Press, New York, states on page 1024:
"Polyimides, produced by the chemical reaction of an aromatic dianhydride and an aromatic diamine, were the first of the aromatic thermally stable polymers introduced in the mid-1950's. Polyimides did not behave as thermoplastics even though they had linear structures. Polymer backbones comprised of rigid, inherently stable, aromatic phenylene and imide rings imparted polyimides with excellent thermal oxidative properties and at the same time made them exceedingly difficult to process because of their high and sometimes indeterminate melting points." PA0 (A) "It is well known that compatible polymer blends are rare". Wang and Cooper, Journal of Polymer Science, Polymer Physics Edition, Vol. 21, p. 11 (1983). PA0 (B) "Miscibility in polymer-polymer blends is a subject of widespread theoretical as well as practical interest currently. In the past decade or so, the number of blend systems that are known to be micsible has increased considerably. Moreover, a number of systems have been found that exhibit upper and lower critical solution temperatures, i.e., complete miscibility only in limited temperature ranges. Modern thermodynamic theories have had limited success to date in predicting miscibility behavior in detail. These limitations have spawned a degree of pessimism regarding the likelihood that any practical theory can be developed that can accommodate the real complexities that nature has bestowed on polymer-polymer interactions." Kambour, Bendler, Bopp, Macromolecules, 1983, 16, 753. PA0 (C) "The vast majority of polymer pairs form two-phase blends after mixing as can be surmised from the small entropy of mixing for very large molecules. These blends are generally characterized by opacity, distinct thermal transitions, and poor mechanical properties. However, special precautions in the preparation of two-phase blends can yield composites with superior mechanical properties. These materials play a major role in the polymer industry, in several instances commanding a larger market than either of the pure components." Olabisi, Robeson, and Shaw, Polymer-Polymer Miscibility, 1979, published by Academic Press, New York, N.Y., p. 7. PA0 (D) "It is well known that, regarding the mixing of thermoplastic polymers, incompatibility is the rule and miscibility and even partial miscibility is the exception. Since most thermoplastic polymers are immiscible in other thermoplastic polymers, the discovery of a homogeneous mixture or partially miscible mixture of two or more thermoplastic polymers is, indeed, inherently unpredictable with any degree of certainty; for example, see P. J. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953, Chapter 13, p. 555." Younes, U.S. Pat. No. 4,371,672. PA0 (E) "The study of polymer blends has assumed an ever increasing importance in recent years and the resulting research effort has led to the discovery of a number of miscible polymer combinations. Complete miscibility is an unusual property in binary polymer mixtures which normally tend to form phase-separated systems. Much of the work has been of a qualitative nature, however, and variables such as molecular weight and conditions of blend preparation have often been overlooked. The criteria for establishing miscibility are also varied and may not always all be applicable to particular systems." Saeki, Cowie and McEwen, Polymer, 1983, vol. 25, January, p. 60. PA0 "The most commonly used method for establishing miscibility in polymer-polymer blends or partial phase mixing in such blends is through determination of the glass transition (or transitions) in the blend versus those of the unblended constituents. A miscible polymer blend will exhibit a single glass transition between the Tg's of the components with a sharpness of the transition similar to that of the components. In cases of borderline miscibility, broadening of the transition will occur. With cases of limited miscibility, two separate transitions between those of the constituents may result, depicting a component 1-rich phase and a component 2-rich phase. In cases where strong specific interactions occur, the Tg may go through a maximum as a function of concentration. The basic limitation of the utility of glass transition determinations in ascertaining polymer-polymer miscibility exists with blends composed of components which have equal or similar (&lt;20.degree. C. difference) Tg's, whereby resolution by the techniques to be discussed of two Tg's is not possible." PA0 "Perhaps the most unambiguous criterion of polymer compatibility is the detection of a single glass transition whose temperature is intermediate between those corresponding to the two component polymers." PA0 hydroquinone, PA0 4,4'-dihydroxybenzophenone, PA0 4,4'-dihydroxybiphenyl, and PA0 4,4'-dihydroxydiphenyl ether. PA0 4-(4'-chlorobenzoyl)phenol, PA0 4-(4'-fluorobenzoyl)phenol, PA0 4,4'-difluorobenzophenone, PA0 4,4'-dichlorobenzophenone, PA0 4-chloro-4'-fluorobenzophenone, ##STR25##
According to T. P. Gannett et al., in U.S. Pat. No. 4,485,140, the polyimide of the structural formula: ##STR2## where R.sub.5 and R.sub.6 are --CH.sub.3 or --CF.sub.3, is typical of aromatic polyimides which are generally infusible. According to Alberino et al, U.S. Pat. No. 3,708,458, a polyimide having recurring units of the formula: ##STR3## "possesses highly useful structural strength properties but . . . is difficult to mold, by compression at elevated temperatures, because of its relatively poor floor properties in the mold". The patentees developed a polyimide to overcome, to some extent, these difficulties by including in the polymer backbone a certain proportion of the reaction product of 3,3',4,4'-benzophenone tetracarboxylic dianhydride with 2,4- or 2,6-toluene diamine (or the corresponding diisocyanates). The copolymers were regarded as having better flow properties in the mold even though such difficult molding procedures as "sintering or hot processing" were the criteria used.
Thus, it can be said that aromatic polyimides in general do not lend themselves easily to melt fabrication except perhaps by compression molding.
Recently, the processability of polyimides has been improved by blending or alloying them with other resins which are themselves more easily melt processable by virtue of being more easily thermoformed and injection molded. For example, U.S. Pat. No. 4,293,670 to Robeson et al. discloses blends of polyarylether resins and polyetherimide resins having excellent mechanical compatibility and good impact strength and environmental stress crack resistance. U.S. patent application Ser. No. 537,042 filed on Sept. 29, 1983 in the name of J. E. Harris et al., assigned to the present assignee, describes blends of a select polyarylketone and a polyetherimide. U.S. patent application Ser. No. 626,105 filed on June 29, 1984 in the name of J. E. Harris et al., assigned to the present assignee, described blends of a polyamideimide and a poly(aryl ether ketone).
Japanese Patent Publications 59/184,254 (Oct. 19, 1984) and 84/187,054 (Oct. 24, 1984), both to Toray Co., Ltd., describe blends of poly(amide-imides), polyamides, and poly(ether-imides) with crystalline poly(aryl ether ketones). According to these publications, the poly(amide-imides) may contain up to 70 mole percent of a polyimide. The addition of the foregoing polymers to poly(aryl ether ketones) is stated to improve the heat deformation temperature as measured according to ASTM method D-648. It is obviously assumed that the resins in question have a Tg above 150.degree. C., and preferably, above 170.degree. C.
However, the Japanese publications do not cover any of the amide and/or imide-containing polymers of the instant invention. A possible miscibility and the resulting good properties of a blend of a poly(amide-imide) or a polyimide and of a poly(aryl ether ketone) must, therefore, be considered as purely speculative from the point of view of the above-mentioned publications.
Also, polyimides in general, do not necessarily improve the heat deformation point, or heat deflection (distortion) temperatures, as sometimes referred to, of poly(aryl ether ketones). For example, J. E. Harris et al. in U.S. patent application Ser. No. 716,401 filed on Mar. 27, 1985, assigned to the same assignee as this application, describe that a blend of 25 parts by weight of the polyimide of the formula: ##STR4## and 75 parts by weight of the poly(aryl ether ketone) of the formula: ##STR5## has a lower heat deflection temperature (151.degree. C.) than the poly(aryl ether ketone) itself (160.degree. C.), even though this polyimide clearly meets the criteria of the foregoing Japanese publication since its Tg of 317.degree. C. is well above their preferred value of 170.degree. C.
The polyimide blends with poly(aryl ether ketones) described in U.S. patent application Ser. No. 716,401 are different from the blends of the present invention; indeed the former blends are immiscible (two phase), while the imide-containing polymers of the present invention yield miscible blends with poly(aryl ether ketones). Miscibility is highly unexpected for a blend of two polymers and is generally not predictable.
In the field of miscibility or compatibility of polymer blends, the art has found predictability to be unattainable, even though considerable work on the matter has been done. According to authorities:
Thus, miscible polymer blends are not common. The criteria for determining whether or not two polymers are miscible are now well established. According to Olabisi, et al., Polymer-Polymer Miscibility, 1979, published by Academic Press, New York, N.Y., p. 120.
W. J. MacKnight et al., in Polymer Blends, D. R. Paul and S. Newman, eds, 1978, published by Academic Press, New York, N.Y., state on page 188:
In this passage, it is clear from the omitted text that by compatibility the authors mean miscibility, i.e., single phase behavior. See, for example, the discussion in Chapter 1 by D. R. Paul in the same work.